The invention relates to machines for molding glass, and more particularly to a device for driving a first and second holder mounted displaceably on a glass molding machine in a reciprocating manner.
In known devices of this type (U.S. Pat. No. 3,066,505 A, U.S. Pat. No. 3,021,644 A, U.S. Pat. No. 2,748,536 A and U.S. Pat. No. 1,974,841 A) the journals are each attached to a carriage which can be displaced in a linear manner in a longitudinal plane of the glass molding machine. In both of the first two US patent documents listed above, a rack on the carriage is in engagement with a pinion which is connected to another pinion via a shaft. The other pinion is in engagement with another rack which can be driven in a reciprocating manner by the common drive. In U.S. Pat. No. 2,748,536 A the carriage is driven by a piston-cylinder unit and in U.S. Pat. No. 1,974,841 A it is driven by a driving roller running on a curved track. Due to undesirable tolerances, these devices are expensive, liable to failure and insufficiently precise in their movements.
In the case of a device which is known per se (U.S. Pat. No. 1,911,119 A, FIGS. 3, 8 and 19) the two holders can pivot about a common perpendicular column of the machine. A joint bar is articulated at an articulation point of each holder in the proximity of a mold toot half. The other end of the joint bar is articulated in each case to a crank pin of a crank. The crank is attached to a respective shaft mounted on the machine. The two shafts are rotationally driven in a reciprocating manner by means of a common double-acting piston-cylinder unit via a lever mechanism.
A similar device is known per se from the German patent document 1 704 112, FIGS. 2 to 5. The two shafts in this case, however, are rotationally driven in a reciprocating manner by a common pneumatic rotating cylinder via a spur wheel reducing gear.
It is the object of the invention to improve and simplify the reciprocating driving of the holders.
The above object is achieved by the features of the invention which provides, in one form, a device for driving a first and second holder mounted displaceably on a glass molding machine in a reciprocating manner. Each of the first and second holders has at least one mold tool half, the mold tool half of the first holder and the mold tool half of said second holder cooperating together to form a mold tool for production of a hollow glass object. The first holder has a first articulation point. A first joint bar is articulated to the first holder at the first articulation point and has a second articulation point. A second joint bar is articulated to the first joint bar at the second articulation point which is disposed at a distance from the first articulation point, the second joint bar being articulated to the glass molding machine at a third articulation point which is disposed at a distance from the first articulation point and the second articulation point. A rod is articulated at the second articulation point. A first crank is provided for moving the first holder and a second crank for moving the second holder, the rod being articulated to the first crank at a crank pin which is at a distance from the second articulation point and which is movable in a reciprocating manner. The device also includes first and second toothed wheels, the first crank being connected coaxially to the first toothed wheel and the second crank being connected coaxially to the second toothed wheel. The toothed wheels are rotationally driven by a drive in opposite directions from one another to drive the first and second cranks.
During the process of molding hollow glass objects, forces are generated inside the mold tools, both in the preform molds of the preform mold station and also in the finishing molds of the finishing mold station, which urge the opening of the closed mold tools. Any such opening is undesirable as the molten glass can be pressed into the parting lines of the mold sections as they part from one another. Numerous additional devices are known in the prior art with which the closed mold tools can be forcibly held closed during the molding processes. Such additional devices for holding the tools closed are superfluous in the case of the present invention. With the invention the closed-holding function of the drive is supported by the lever mechanism by which the whole mechanism between the drive and the holders becomes desirably non-linear. The lever mechanisms cause the closed-holding force to be increased when the holders, and therefore the mold tools, are in the closed position. The movement of the holders can be achieved in a known manner either by pivoting or by linear displacement. By means of both toothed wheels and the drive it is possible to form the device in a generally simple, cost-effective and space-saving manner and for the device still to produce extremely precise opening and closing movements for the holders.
Additional features can provide other advantages. For example, the toothed wheels can be formed as a first and a second worm wheel which is in engagement with a common worm that can be rotationally driven in a reciprocating manner by the drive. Additionally, the worm wheels can be in engagement with diametrically opposite sides of the worm. Moreover, the worm can have a longitudinal axis that is disposed in a longitudinal plane of the device. Such features each provide a compact and stable embodiment of the device.
In another embodiment, the toothed wheels can be formed as mutually engaged spur wheels, and a shaft of one of the spur wheels can be rotationally driven in a reciprocating manner by the drive. In accordance with such features, a particularly simple and functionally reliable toothed wheel mechanism is produced. The spur wheels can be toothed in any suitable way, for example with straight or inclined toothing.
In the invention, the drive can comprise an electric servomotor. This permits a very precise programmable control of the closing and opening movements of the holders. To achieve sufficient closed-holding forces the torque of the electric servomotor can remain switched through during the molding processes. Furthermore, the drive can comprise a gear mechanism connected downstream of the electric servomotor. According to this feature, the mechanism can be arranged according to the respective requirements. For example, a reducing gear and/or, for reasons of space, an angular gear may be used.